mcp-scaffold

A generic, plug-and-play MCP (Model Context Protocol) server. Clone it, add your own tools to tools.js, run it, and connect it to Claude, Cursor, or Windsurf. No MCP SDK, no framework, no build step — just Node's built-in http module.

Quick start

git clone https://github.com/abduznik/mcp-scaffold.git
cd mcp-scaffold
npm install   # no dependencies, but keeps npm happy
npm start

mcp-scaffold running on http://localhost:3939/mcp
Registered tools: (none yet — add some in tools.js)

That's expected — tools.js ships with its example tool commented out. See below to turn it on.

Related MCP server: MCP Tools

Try the example tool

Open tools.js. Near the top of the tools array there's a roll_dice example, fully commented out:

export const tools = [
  // ── EXAMPLE TOOL — commented out by default ─────────────────────────────────
  // Uncomment the block below to try a working example (rolls dice). Comment it
  // back out (or delete it) once you're ready to add your own tools instead.
  //
  // {
  //   name: "roll_dice",
  //   ...
  // },
];

Uncomment that block (just the { ... } object — remove the leading // from each line), restart the server, and roll_dice is live:

Registered tools: roll_dice

Comment it back out any time to disable it again — nothing else in the project needs to change either way.

Add your own tool

mcp-server.js is generic plumbing — you shouldn't need to edit it. Everything you touch lives in tools.js:

export const tools = [
  // ...existing tools...

  {
    name: "my_tool",
    description: "One clear sentence describing what it does and when to use it.",
    inputSchema: {
      type: "object",
      properties: {
        arg_one: { type: "string", description: "What this argument is for" },
      },
      required: ["arg_one"],
    },
    handler({ arg_one }) {
      return `You said: ${arg_one}`;
    },
  },
];

Restart the server (npm start) and your tool is live.

The description field matters more than it looks. The model reads it to decide when to call your tool, not just what it does. Be specific about the trigger ("use this when the user asks to...") rather than just naming the function.

Test it before connecting any AI client

Always verify with curl first — if something's broken, this tells you whether the bug is in your server or in the client config.

# initialize
curl -s -X POST localhost:3939/mcp \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize"}'

# tools/list — confirm your tool shows up
curl -s -X POST localhost:3939/mcp \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/list"}'

# tools/call — confirm it actually runs (after uncommenting roll_dice)
curl -s -X POST localhost:3939/mcp \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"roll_dice","arguments":{"sides":20,"count":2}}}'

Connect it to Claude Desktop

Add this to claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "mcp-scaffold": {
      "type": "url",
      "url": "http://localhost:3939/mcp"
    }
  }
}

Restart Claude Desktop. Ask it to do whatever your tool does, in plain language — the model calls your tool on its own when it decides it's relevant.

Deploying it for free (optional)

This server has zero dependencies, so it also runs unmodified on Cloudflare Workers — just wrap the same logic in a fetch(request) export instead of http.createServer. Free tier, no credit card, public URL anyone can connect to.

How it works

• mcp-server.js — generic MCP protocol handler. Answers the three methods every MCP client needs: initialize, tools/list, tools/call. Reads whatever tools are exported from tools.js and wires them up automatically.

• tools.js — where your tools live. Each tool is { name, description, inputSchema, handler }. handler can be sync or async and can return anything that stringifies sensibly — that string is what the model sees back.

License

MIT — do whatever you want with it.